An unusual case is described in which an abdominal wall and thigh abscess was an initial symptom of ascending colon cancer. A 76-year-old woman was referred to our hospital for investigation of fever and abdominal and thigh swelling. Computed tomography revealed a right abdominal wall, retroperitoneal, psoas and thigh abscess formation suspected to be caused by colon perforation. Due to the patient's poor general condition, local drainage of the abscess was performed on the following day of hospitalization. Histological examination of necrotic tissues removed form the retroperitoneal cavity demonstrated adenocarcinoma of the colon. The patient subsequently underwent right hemicolectomy with lymph nodal dissection after 19 days of the drainage procedure and was transferred to another hospital on the 49th day following the second surgery.